Translation of abstract (English)

Individual and collective 1H dipole-dipole interactions yield a new approach for studies of microscopic structures by liquid NMR. The application of the CRAZED pulse sequence (two rf pulses, delay τ, gradient G) generates intermolecular multiple-quantum coherences based on collective 1H dipole-dipole interactions of protons with mutual distance d= π/(γGτ) (correlation distance). d depends on the strength of the gradient and typical values are d=1mm…0,1mm. In principle, the dependence on the distance enables investigation of dimensions of structured samples. In this study we were able to verify the distance-dependency using periodically structured phantoms. It could also be shown that the measured CRAZED-signal is based on the fourier spectra of the structure. According to traditional diffraction experiments information on the wavelengths of the structure can be obtained. To enable MRI studies, different types of CRAZED MR-imaging pulse sequences were implemented on a clinical 1.5-T whole-body scanner. In vivo MR images from the brain of healthy volunteers could be obtained using these sequences. MR imaging based in the CRAZED experiment provides a new image contrast, depending on the mutual distance of selected protons. In different types of biological tissues (e.g. tendon, cartilage, muscle, nerves) individual 1H dipole-dipole interactions are caused by immobilized protons. Restricted mobility is the consequence of bonds or chemical exchange between protons and a macromolecular matrix. The difference between the transverse relaxation times T2 and T2 ρ is used to isolate immobilized protons in MR imaging. These protons provide a new contrast in MR images. The imaging method is based on the signal difference between a synchronized spinecho and „magic sandwich echo“ pulse sequence. Verification of this method was done using agar-gel phantoms. In vivo images could be obtained from the calf of healthy volunteers. MR image contrast based on immobilized protons may provide additional information for diagnosis of diseases in tissues like tendon, cartilage, muscle, and nerves.